Quantum key distribution (QKD) exploits the quantum features of photons to share cryptography keys between two parties in a way that makes any eavesdropping readily apparent. Keys have been exchanged successfully across cities and even between a spacecraft and a ground station. Such feats usually require complex, expensive equipment. Now Feihu Xu and Jian-Wei Pan of the University of Science and Technology of China (USTC) and their collaborators have demonstrated QKD over 403 km of standard optical fiber using off-the shelf lasers [1]. At nearly 48 bits per second (bit/s), their key distribution rate is high enough for some real-world applications.
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